PCA10056 Board Definition

[jleng]

Hi,

I'm using nrf52840 and trying to define the pin mappings for my custom board. In order to do this I'm studying the board definition of pca10056 (pca10056.h).

In that file I saw some definitions are mapped to single pin number, for example 

#define BSP_LED_0   13
#define BUTTON_1    11

.

However, there are also some definitions mapped using the macro 

NRF_GPIO_PIN_MAP(port, pin) (((port) << 5) | ((pin) & 0x1F))

.

My questions are the followings:

1. Just to confirm --- if I want to define a pin, for instance P1.13, I should do #define MY_PIN NRF_GPIO_PIN_MAP(1, 13), correct?

2. By looking at this macro, it seems that it should be used when I want to map to a pin on port 1. If it's on port 0, I can simply use the pin number (such as BSP_LED_0 and BUTTON_1 above)?

3. If my second point holds, why am I seeing some pins are also mapped, for example, using NRF_GPIO_PIN_MAP(0, 27)? Wouldn't this be redundant or is there something I've missed?

Thank you!

[Jørgen Holmefjord]

Hi,

1. NRF_GPIO_PIN_MAP() is a utility-macro that can be used to define the correct pin numbers. You are not forced to use this, but it will likely make the code more readable. When a GPIO is assigned to a peripheral pin, pins on port 1 are given by setting bit 5 of the register. This is equal to adding 32 to the pin number, i.e. P1.13 would be 32+13=45. The output from the NRF_GPIO_PIN_MAP() macro would be the same.
2. It can be used for pins on both port 0 and port 1. The port argument (0 or 1) is simply left-shifted 5 places.
3. As mentioned before, it is not strictly necessary, but it increases readability of the code. It may also help for future maintenance/compatibility to be consistent with use of macros like this.

Best regards,
Jørgen